1. Field of the Invention
The present invention relates to an electronic component, a manufacturing method thereof, an aggregate electronic component, a mounting structure of an electronic component, and an electronic device, and more particularly, the present invention relates to an improvement in the formation and structure of an external terminal electrode.
2. Description of the Related Art
A prior art which is related to the present invention is disclosed in Japanese Unexamined Patent Application Publication No. 08-37251. Hereinafter, this is referred to as the xe2x80x9cfirst prior artxe2x80x9d.
This first prior art relates to a laminated electronic component and a manufacturing method therefor. The first prior art is characterized in that first, an aggregate electronic component is produced, and then, a plurality of electronic components are produced from the aggregate electronic component by dividing the aggregate electronic component along dividing lines.
More specifically, a laminated body is produced by laminating a plurality of dielectric sheets having via-hole conductors formed therein, then through-holes passing through the laminated body are formed at locations of the via-hole conductors, thereby the via-hole conductors are divided, and a portion of each of the via-hole conductors is caused to be exposed to the inner surface of the through-hole. Next, by dividing the laminated body along dividing lines passing through the through-holes, electronic components are removed and produced such that each of the electronic components has external terminal electrodes each constituted of a portion of the via-hole conductor.
In accordance with the first prior art, external terminal electrodes can be easily formed even if the arrangement pitch is fine, and the characteristics of the individual electronic components which exist at the stage of a laminated body when it is in the state of an aggregate electronic component, can be measured.
Another prior art which is related to the present invention is disclosed in Japanese Unexamined Patent Application Publication No. 06-96992. Hereinafter, this is referred to as the xe2x80x9csecond prior artxe2x80x9d.
This second prior art also relates to a laminated electronic component and a manufacturing method therefor. As in the case of the first prior art, the second prior art is characterized in that firstly an aggregate electronic component is produced, and that a plurality of electronic components is removed from the aggregate electronic component by dividing the aggregate electronic component along dividing lines.
More specifically, a laminated body is produced by laminating a first dielectric sheet which has via-hole conductors defining external terminal electrodes formed therein, and a second dielectric sheet which does not via-hole conductors formed therein, then grooves are formed so as to divide the via-hole conductors, and thereby a portion of each of the via-hole conductors is caused to be exposed to the inner surface of the groove. Next, by dividing the laminated body along the grooves, electronic components are produced such that each of the electronic components are provided with external terminal electrodes each constituted of a portion of the via-hole conductor.
In accordance with the second prior art, as in the case of the first prior art, external terminal electrodes can be easily formed even if the arrangement pitch is fine, and measurement of the characteristics of the individual electronic components can be measured at the stage of a laminated body in the state of an aggregate electronic component.
In the first prior art, there are provided external terminal electrodes each having a length that is equivalent to that of the through-hole formed in the laminated body. In contrast, in the second prior art, the external terminal electrodes have a length that is within the range of the depth of each of the grooves, the depth of each of the grooves corresponding to a portion of the thickness of the laminated body.
However, each of the first and second prior arts presents problems to be solved.
First, in the first prior art, since each of the external terminal electrodes has a length that is equivalent to that of each of the through-holes formed in the laminated body, the external terminal electrodes are arranged so as to reach both of first and second main surface. Therefore, for example, when using the first main surface as a mounting surface for mounting components, a predetermined space must be provided between external terminal electrodes and connection terminals for the mounted components when soldering the mounded component, in order to prevent short circuits between the mounted components and the external terminal electrodes. This greatly reduces the area in which mounted components can be mounted.
Likewise, in the case where this electronic component is mounted on a mother circuit board, when the second main surface is arranged to face the mother circuit board, it is necessary to prevent solder or other such connecting material used for connecting external terminal electrodes and the mother circuit board from causing an undesirable electrical short circuit between wiring conductors and the external terminal electrodes on the second main surface. For this purpose, a predetermined space must be provided between the wiring conductors and the external terminal electrodes. This also leads to a reduction in the mountable area for wiring conductors on the second main surface.
Furthermore, when the electronic component is a ceramic electronic component that is manufactured through a firing process, irregularities or uneven portions occur in the vicinity of external terminal electrodes on the main surfaces of the electronic component due to a difference in the shrinkage during firing between the via-hole conductors and the ceramic. As a result, when wire-bonding mounting or flip-chip mounting is performed, each of which is usually required to provide a coplanarity of not more than 20 xcexcm, it is impossible to properly perform mounting in the vicinity of the external terminal electrodes. This also causes a reduction in the mountable area for mounted components.
When an electronic component is mounted on a mother circuit board via solder, solder fillets are formed between the external terminal electrodes of the electronic component and the connection terminals of the mother circuit board. When the electronic component is used for a high-frequency application, these solder fillets function as inductance components which cannot be ignored, and hence, the control over the height of fillets is important. The height of the fillet is determined by the amount of solder used and the wettability of the solder with respect to the surface of the external terminal electrodes. However, if the external terminal electrodes are provided so as to pass through in the thickness direction of the electronic component, the height of fillets will be difficult to control, and hence, when the electronic component is used for a high-frequency application, the inductance component due to solder fillets varies.
The above-described problems which are experienced with the first prior art can be solved to some extent by using the method of the second prior art. This is because, in accordance with the second prior art, the external terminal electrode is not arranged so as to pass through in the thickness direction of the electronic component, but is arranged so as to reach only one of the main surfaces.
However, the second prior art has the following problem.
Even at the stage of a laminated body in the state of an aggregate electronic component, in order to allow characteristics of individual electronic components to be measured, external terminal electrodes for the individual electronic components are made to be independent of one another by dividing the via-hole conductors. Such division of the via-hole conductors is achieved by forming grooves along dividing lines for dividing via-hole conductors so as to remove and separate the individual electronic components.
However, such grooves can produce or cause inadvertently breakable places in an aggregate electronic component, and the aggregate electronic component can be undesirably broken during the process of treating the aggregate electronic component to perform the operation of measuring characteristics thereof, or other processing steps. Such a breakage is more prone to occur when the thickness is reduced to e.g. about 0.8 mm, under the circumstance where the thinning of electronic component is progressing.
In order to overcome the problems described above, preferred embodiments of the present invention provide an electronic component, a manufacturing method therefor, and an aggregate electronic component all of which solve the above-described problems by forming an electronic device using of a mounting structure of an electronic component.
According to a first preferred embodiment of the present invention, a method for manufacturing an electronic component includes the steps of producing a laminated body by laminating a first dielectric-layer portion which has a first thickness and which has via-hole conductors defining external terminal electrodes formed therein, and a second dielectric-layer portion which has a second thickness and which does not have via-hole conductors formed therein at the portions where the via-hole conductors of said first dielectric-layer portion are positioned, forming through-holes which pass through mutually opposed first and second main surfaces of the laminated body, at the portions where the via-hole conductors of the laminated body are positioned, and thereby causing a portion of each of the via-hole conductor to be exposed at the inner surface of the through-hole, and dividing the laminated body along dividing lines passing through the through-holes so as to remove individual electronic components each including external terminal electrodes each of which includes a portion of the via-hole conductor.
In the method of manufacturing an electronic component according to this preferred embodiment of the present invention, it is preferable that the laminated body is an aggregate electronic component which is arranged so that a plurality of electronic components can be removed therefrom by dividing the laminated body along the dividing lines. In this case, the step of forming through-holes and the step of dividing the laminated body are performed on the aggregate electronic component, and in the step of forming through-holes, through-holes are formed so as to each divide the via-hole conductors. By dividing this aggregate electronic component, a plurality of the electronic components is removed from the aggregate electronic component.
In the above-described preferred embodiment, it is preferable that the step of measuring characteristics of each of the electronic components in the state of the aggregate electronic component is performed before the step of dividing the aggregate electronic component.
When each of the above-described first and second dielectric-sheets are constituted of ceramic green sheets, the manufacturing method for an electronic component further includes the step of firing the laminated body.
In the manufacturing method for an electronic component in accordance with the present preferred embodiment of the present invention, the first thickness preferably is substantially equal to the thickness of the laminated body. It is preferable that the first thickness be about 0.9 times or below the sum of the first and second thicknesses of the respective first and second dielectric-layers.
Preferably, the above-described step of forming through-holes is performed so that the state in which the electronic components are connected to the peripheral portions is remaining, at the portion having a length not less than about 50% of the length of the dividing lines for removing the electronic components.
Other preferred embodiments of the present invention provide an electronic component obtained by the above-described manufacturing method.
Furthermore, additional preferred embodiments of the present invention provide an electronic component, which includes an electronic component body having a first and second main surfaces opposed to each other, and side surfaces connecting the first and second main surfaces. Grooves are provided in the side surfaces of this electric component, and each of the grooves has a first length and passes through from the first main surface to the second surface. Each of the grooves also includes a recess which has a second length that is less than the first length and also has an opening formed on the bottom surface of the groove and extending along the longitudinal direction of the groove. In the recess, there is provided an external terminal electrode having the second length.
In the above-described electronic component, it is preferable that the second length is about 0.9 times or below the dimension of the first length.
With regard to the peripheral direction of the side surfaces of the electronic component body, it is preferable that the length of the portion at which there is no groove formed, be not less than about 50% of the length of the overall periphery of the side surfaces.
In the electronic component in accordance with this preferred embodiment of the present invention, the external terminal electrode may be arranged so as to reach the second main surface. Alternatively, the external terminal electrode may be arranged so as not to reach either of the first and second main surfaces.
Also, in the electronic component in accordance with other preferred embodiments of the present invention, the electronic component body may have a lamination structure, and simultaneously may have an inner circuit element.
Furthermore, the electronic component in accordance with preferred embodiments of the present invention may further include a surface mounted device which is mounted on at least one of the first and second main surfaces.
Moreover, the electronic component in accordance with other preferred embodiments of the present invention may further include a metallic cover arranged so as to cover the surface mounted device. In this case, it is preferable that the metallic cover have claws arranged to be disposed in at least one of the grooves, and that these claws be connected to at least one of the external terminal electrodes.
Preferably, the electronic component in accordance with various preferred embodiments of the present invention is used for high-frequency applications.
In accordance with another preferred embodiment of the present invention, an electronic component includes an electronic component body having first and second main surfaces opposed to each other, and side surfaces connecting the first and second main surfaces. In this electronic component, at least one of the first and second main surfaces is a mounting surface on which a surface mounted device is mounted, and in the side surfaces, there are formed grooves each of which has a first length and which passes through from the first main surface to the second surface. In each of the grooves, an external terminal electrode having a second length that less than the first length is provided so as to extend in the longitudinal direction thereof.
Other preferred embodiments of the present invention provide an aggregate electronic component which has first and second main surfaces opposed to each other, and which is arranged so as to remove therefrom a plurality of electronic components by dividing the aggregate electronic component in a direction that is substantially perpendicular to the main surfaces, along predetermined dividing lines.
In the aggregate electronic component in accordance with this preferred embodiment of the present invention, there are provided via-hole conductors each of which has an axial direction size smaller than the thickness size between the first and second main surfaces, and each of which is provided so as to straddle the dividing line, and through-holes passing through the first and second main surfaces, are provided so as to each divide the via-hole conductors. Also, there are provided external terminal electrodes, each including a divided portion of the via-hole conductor that is divided by the through-hole.
In the above-described aggregate electronic component, preferably, the axial direction size of the via-hole conductor is about 0.9 times or below the thickness dimension between the first and second main surfaces.
In this aggregate electronic component, it is preferable that the length of the portion where no through-hole is provided, of the dividing lines for removing the electronic components, be not less than about 50% of the overall length of the dividing lines for removing the electronic components.
This aggregate electronic component may further include a surface mounted device which is mounted on at least one of the first and second main surfaces thereof.
Preferred embodiments of the present invention also provide a mounting structure wherein an electronic component as described above is been mounted on a mother circuit board having connection terminals.
In the mounting structure in accordance with various preferred embodiments of the present invention, the external terminal electrodes of the electronic component and the connection terminals of the mother circuit board are connected via solder fillets, and the height of the solder fillets is defined by the second length of the external terminal electrode.
Preferred embodiments of the present invention also provide an electronic device provided with an electronic component as described above.
Other elements, characteristics, features, and advantages of the present invention will be clear from the following detailed description of preferred embodiments of the present invention in conjunction with the accompanying drawings.